I think the guy who filed #9953 gave up too easily. :) I'm seeing the same error message in Angular 1.3. I'm using a modified version of the angular-ui bootstrap datepicker that uses ng-if to only render the control if it is open, and so I'm reasonably certain the analysis by @caitp in that issue is exactly the problem for me. If I add the following at line 1201 in angular-animate.js after the call to extractElementNode(), the error message goes away:

if (!elementNode) {
    done();
    return;
}

There's also a comment by @matsko there about refactoring some code into animationsDisabled() after #8092 is fixed, which it now is, so I'm not sure if there's some more work to be done in that area.

I have not noticed any consequences to this, since presumably we can't do much to animate a DOM element that isn't there...